Method for fabricating electric interconnections and interconnection substrate having electric interconnections fabricated by the same method

ABSTRACT

An oxide film is formed on an insulating substrate by means of a wet type film forming technique such as a sol-gel method, a chemical deposition method or a liquid phase deposition method. Next, the oxide film is patterned according to the shape of interconnections. Then, a metal film made of Ni is formed on an oxide film pattern by such a wet type film forming technique as a wet type plating method. Further, a metal film made of Au that has a low resistance is laminated on the metal film made of Ni by electroless plating, and a metal film made of Cu that has a low resistance and is low cost is laminated on the Au film by electroplating. Thus, by the above method for manufacturing electric interconnections, a large-area interconnection substrate for a display device and an image detector is able to be fabricated at low cost without using a vacuum film forming apparatus.

BACKGROUND OF THE INVENTION

The present invention relates to a method for fabricating electricinterconnections to be used for electronic circuit boards of electricequipment such as a flat panel display or a two-dimensional imagedetector, further relates to an interconnection substrate applicable toa variety of electronic devices, relates to display devices such as aliquid crystal display (LCD), a plasma display (PDP), an electrochromicdisplay (ECD), an electroluminescent display (ELD) and relates to animage detector using light or radial rays.

Conventionally, in a flat panel display represented by the liquidcrystal display, display material such as liquid crystal or electricdischarge gas is normally held between a pair of substrates, and avoltage is applied to this display material. In this stage, electricinterconnections made of conductive material are provided at least onone substrate.

For example, in the case of an active matrix drive type display, gateelectrodes and data electrodes are arranged in a matrix form on onesubstrate (active matrix substrate) of a pair of substrates that holdthe display material between them, and a thin film transistor (TFT) anda pixel electrode are arranged at each intersection. These gateelectrodes and data electrodes are normally made of a metal materialsuch as Ta, Al or Mo and formed into a film by a dry film forming methodsuch as a sputtering method.

There has also been developed a flat panel type two-dimensional imagedetector obtained by combining an active matrix substrate having aconstruction similar to that of the aforementioned active matrix drivetype display with a photodetector element or an X-ray detecting element.The details of the two-dimensional image detector are disclosed in thereference documents of “L. S Jeromin, et al., “Application of a-SiActive-Matrix Technology in X-Ray Detector Panel”, SID 97 DIGEST,p.91-94, 1997”, “Japanese Patent Laid-Open Publication No. HEI 6-342098”and others.

If it is tried to increase the area and improve the definition of theflat panel display or the two-dimensional image detector of the abovekind, then the resistance and parasitic capacitance of the electricinterconnections increase as the drive frequency increases, andaccordingly, the delay of the drive signal emerges as a serious problem.

Therefore, in order to solve the problem of this drive signal delay, itis tried to use low electric resistance Cu (bulk resistivity is 1.7μΩ·cm) as an interconnection material instead of the conventionalinterconnection materials of Al (bulk resistivity is 2.7 μΩ·cm), α-Ta(bulk resistivity is 13.1 μΩ·cm) and Mo (bulk resistivity is 5.8 μΩ·cm).There is a disclosure of the examination of a TFT liquid crystal display(TFT-LCD) employing Cu as a gate electrode material in, for example, thereference of “Low Resistance Copper Address Line for m TFT-LCD”(JapanDisplay '89 p.498-501). This reference document states clearly thenecessity for improving the adhesion by interposing a metal film of Taor the like on the groundwork since the Cu film formed by the sputteringmethod has poor adhesion to the groundwork glass substrate.

However, in the case of the interconnection structure in which a metalfilm of Ta or the like is provided as an interposition on theabove-mentioned groundwork, the Cu film and the groundwork metal film ofTa or the like need individual dry film forming processes and etchingprocesses, and this disadvantageously causes an increased number ofprocesses and cost increase.

In view of the above, the prior art reference of Japanese PatentLaid-Open Publication No. HEI 4-232922 proposes electric interconnectionfabricating method for using a transparent electrode made ofindium-tin-oxide (ITO: tin-added indium oxide) or the like as agroundwork film and forming by a technique of plating the surface of thegroundwork film with a metal film of Cu or the like. According to thistechnique, there is clearly stated the effect of allowing Cuinterconnections to be efficiently formed even in a large area since theplating metal can be formed as a film selectively on the ITO film andtherefore the patterning process is necessary for only the ITO film ofthe transparent electrode. There is also stated a structure By forinterposing a metal film of Ni or the like having a good adhesionproperty between ITO and Cu.

There has also been proposed electric interconnection fabricating methodfor forming a metal film of Ni, Au, Cu or the like on a patterned ITOfilm by a plating technique for the various purposes of reducing theprocesses of the active matrix substrate, reducing the resistance of thetransparent electrode of a simple matrix type liquid crystal displaydevice, increasing the solder wettability on the ITO film and so onbesides the electric interconnection fabricating method described in theaforementioned prior art reference of Japanese Patent Laid-OpenPublication No. HEI 4-232922 (refer to, for example, the prior artreference documents of Japanese Patent Laid-Open Publication No. HEI2-83533, Japanese Patent Laid-Open Publication No. HEI 2-223924,Japanese Patent Laid-Open Publication No. SHO 62-288883 and JapanesePatent Laid-Open Publication No. HEI 1-96383).

However, in the case of the electric interconnection fabricating methodusing ITO for the groundwork, the metal film is formed by the platingtechnique using no vacuum film forming apparatus. However, the ITO filmthat becomes the groundwork of the metal film is formed still by avacuum film forming apparatus of the sputtering method or the vacuumdeposition method. This leads to the problem that a sufficient costreduction effect cannot be obtained and the method cannot easily copewith a large-area substrate.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide anelectric interconnection fabricating method, an interconnectionsubstrate, a display device and an image detector, which is able to befabricated at low cost and to easily cope with a large-area substrateusing no vacuum film forming apparatus.

In order to achieve the aforementioned object, the present inventionprovides an electric interconnection fabricating method comprising: anoxide film forming process for forming an oxide film on an insulatingsubstrate by a first wet type film forming technique; and a metal filmforming process for forming a metal film on the oxide film by a secondwet type film forming technique.

According to the above invention, the electric interconnections havingthe laminate structure formed of the metal film and the oxide film canbe obtained using no vacuum film forming apparatus, and the sufficientcost reduction effect can be obtained by comparison with theconventional electric interconnection fabricating method. The first andsecond wet type film forming techniques can easily cope with thelarge-area substrate since the first and second wet type film formingtechniques can more easily form a large-area film than the vacuum filmforming technique. The electric interconnections having a laminatestructure formed of the metal film and the oxide film can be obtainedwithout using any vacuum film forming apparatus. Therefore, electricinterconnections can be easily formed on an insulating substrate (apolymer film, for example) or the like made of an organic materialbesides a glass substrate having excellent vacuum resistance and heatresistance. Furthermore, electric interconnections can be formed withhigh productivity according to a roll-to-roll system using a long filmbase material.

In one embodiment of the present invention, the electric interconnectionfabricating method further comprises a patterning process for patterningthe oxide film according to a specified shape between the oxide filmforming process and the metal film forming process.

According to the above embodiment, the metal film formed through themetal film forming process can be selectively formed only on the oxidefilm patterned according to a specified shape through the patterningprocess. Therefore, the metal film is formed only in the requiredportion by comparison with the case where an oxide film and a metal filmare formed on the entire surface of an insulating substrate andthereafter both the films are patterned. Accordingly, the patterning ofthe metal film becomes unnecessary, and also no waste of the metal filmmaterial is generated.

In one embodiment of the present invention, a precursor of the oxidefilm has photosensitivity and the patterning process for patterning theoxide film according to the specified shape comprises a process forapplying light to the precursor of the oxide film.

According to the above embodiment, neither resist coating process norresist removing process is required between the oxide film formation andthe patterning process, and therefore, the producibility can beimproved.

In one embodiment of the present invention, the first wet type filmforming technique used for the oxide film forming process is a sol-gelmethod.

The above-mentioned sol-gel method is a sort of wet type film formingtechnique and includes the processes of using a metal organic compoundor an inorganic compound as a solution, promoting the hydrolysis andpolycondensation of a compound in the solution so as to fix a sol as agel and forming an oxide solid through the heating of the gel. Accordingto the above embodiment, the oxide film can be easily formed by merelycoating a sol-gel solution on the insulating substrate of glass or thelike and sintering the same by the sol-gel method using no vacuum filmforming apparatus. Furthermore, according to the sol-gel method, therecan be formed a multi-porous oxide film in which minute holes exist in anetwork style as compared with the smooth surface of the oxide filmformed by the vacuum film forming apparatus. Therefore, if the oxidefilm obtained by the sol-gel method is plated with a metal film, thenthe minute holes of the oxide film produce an anchor effect, allowing aplating film of a very good adhesion property to be obtained. This alsoallows electroless Cu plating to be effected on an ITO film, which hasconventionally been difficult.

In one embodiment of the present invention, the first wet type filmforming technique used for the oxide film forming process is either achemical deposition method or a liquid phase deposition method.

The chemical deposition method is the method of immersing an insulatingsubstrate in an aqueous solution and depositing an oxide film on theinsulating substrate through a redox reaction in the aqueous solution.The liquid phase deposition method (LPD method) is the method ofdepositing an oxide film on an insulating substrate through a hydrolyticequilibrium reaction of a metallic fluoro-complex or hydrosilicofluoricacid. According to the embodiment, an oxide film can be easily formed bymerely immersing an insulating substrate in an aqueous solution by thechemical deposition method or the liquid phase deposition method usingno vacuum film forming apparatus. According to the oxide film obtainedby the chemical deposition method, crystal grains grow around a core ofa metal catalyst made to adhere to the surface of the insulatingsubstrate. Therefore, the surface becomes more undulated than that ofthe oxide film formed by the vacuum film forming apparatus. Therefore,if the oxide film obtained by the chemical deposition method is platedwith a metal film, then the surface unevenness of the oxide filmproduces an anchor effect, allowing a plating film of a very goodadhesion property to be obtained.

In one embodiment of the present invention, the second wet type filmforming technique used for the metal film forming process is a wet typeplating method.

According to the above embodiment, in the case of the electroplating ofthe wet type plating technique that is classified roughly intoelectroplating and electroless plating, a metal film is deposited on thesurface of the cathode by arranging a metal that serves as an anode andthe cathode (electrode subjected to plating) in a plating liquid inwhich metal ions are dissolved and flowing a direct current through theplating liquid. Therefore, if the oxide film of the groundwork formedthrough the oxide film forming process has conductivity, then it isallowed to deposit a metal film on only the oxide film by making theoxide film serve as a cathode. In the case of the electroless plating(reduction plating or displacement plating), a metal film can bedeposited flowing no current through the plating liquid. Therefore, ametal film can be deposited regardless of the presence or absence of theconductivity of the oxide film of the groundwork formed through theoxide film forming process. A plating film having a great film thicknesscan be formed even in a large area since a current distribution densityinfluences less than in the case of electroplating. Furthermore, byperforming the process for making the catalyst adhere selectively toonly the surface of the oxide film in this stage, a metal film can alsobe deposited selectively on only the oxide film. Thus, by using the wettype plating method for the wet type film forming technique of the metalfilm forming process, a metal film can be easily formed using no vacuumfilm forming apparatus.

In one embodiment of the present invention, the oxide film has a platingcatalyst.

According to the above embodiment, the process of providing the platingcatalyst can be eliminated when forming a metal film on the oxide filmby electroless plating in a subsequent process.

In one embodiment of the present invention, the oxide film is aconductive oxide film.

According to the above embodiment, a metal film can be formed on theconductive oxide film by electroplating by providing the oxide film by aconductive oxide film.

In one embodiment of the present invention, the conductive oxide filmhas transparency.

According to the above embodiment, by providing the oxide film by aconductive oxide film having transparency, the transparent electrodeprovided for each pixel of, for example, a liquid crystal display deviceor a two-dimensional image detector besides the electricinterconnections can be formed of the same transparent conductive oxidefilm, allowing the reduction in number of processes to be achieved.

In one embodiment of the present invention, the conductive oxide film isa film to be used for the electric interconnections and an applicationother than the electric interconnections and is formed of an identicalmaterial on the insulating substrate through an identical process.

According to the above embodiment, if it is required to form a film of atransparent conductive film (for example, a transparent electrodeprovided for each pixel) other than the use of electric interconnectionsas in the liquid crystal display device or a two-dimensional imagedetector, then a transparent conductive oxide film formed of anidentical material through an identical process can be used for theelectric interconnections and as a film for the use other than theelectric interconnection use. This allows the reduction in number ofprocesses and efficient fabrication of electric interconnections.

In one embodiment of the present invention, the metal film is either asingle layer film made of any one of nickel (Ni), copper (Cu) and gold(Au) or a multi-layer film including at least one layer of a singlelayer film made of any one of nickel (Ni), copper (Cu) and gold (Au).

According to the above embodiment, the Ni film can be formed on theoxide film (ITO film etc.) with a good adhesion property, andelectroless plating can be performed selectively on only the oxide film(ITO film etc.). Further, Cu and Au have a low specific resistance, andthis can achieve electric interconnections having a low resistance. Inparticular, by forming an Ni film on the oxide film (ITO film) andfurther forming a Cu, Au or Cu/Au film on the Ni film, then electricinterconnections having a low resistance and a good adhesion propertycan be provided.

In one embodiment of the present invention, an interconnection substratecomprises electric interconnections of a laminate structure including anoxide film formed on an insulating substrate by a first wet type filmforming technique and a metal film formed on the oxide film by a secondwet type film forming technique.

According to the interconnection substrate of one inventive aspect,electric interconnections having a laminate structure formed of a metalfilm and an oxide film can be obtained without using any vacuum filmforming apparatus, allowing a sufficient cost reduction effect to beobtained as compared with the case where electric interconnectionsformed by the conventional fabricating method is used. The first andsecond wet type film forming techniques can easily cope with alarge-area substrate since the film formation in a large area can beeasily achieved by comparison with the vacuum film forming technique.Furthermore, electric interconnections having the laminate structureformed of the metal film and the oxide film can be obtained withoutusing any vacuum film forming apparatus. Therefore, electricinterconnections can be easily formed on an insulating substrate (forexample, a polymer film) or the like made of an organic material besidesthe glass substrate having excellent vacuum resistance and heatresistance. Furthermore, electric interconnections can be formed withgood productivity according to a roll-to-roll system using a very longfilm material taking advantage of the merit that no vacuum system isused.

In one embodiment of the present invention, the oxide film is patternedaccording to a shape of interconnections and the metal film is formedselectively on the patterned oxide film.

According to the above embodiment, the metal film is formed only in thenecessary portion by comparison with the case where the oxide film andthe metal film are both formed on the entire surface of the insulatingsubstrate and thereafter patterned according to the shape ofinterconnections. Therefore, the metal film patterning process becomesunnecessary, and also no waste of the metal film material is generated.

In one embodiment of the present invention, the precursor of the oxidefilm has photosensitivity.

According to the above embodiment, the oxide film can be patternedaccording to the specified shape by applying light to the precursor ofthe oxide film, and neither resist coating process nor resist removingprocess is needed between oxide film formation and the patterning, andtherefore, the producibility can be improved.

In one embodiment of the present invention, the oxide film is amulti-porous film.

According to the above embodiment, if the surface of the multi-porousoxide film is plated with a metal film, then the minute holes of theoxide film produce an anchor effect, allowing a plating film of a verygood adhesion property to be obtained. This allows electroless Cuplating to be effected on an ITO film, which has conventionally beendifficult.

In one embodiment of the present invention, the oxide film is a filmhaving surface unevenness.

According to the above embodiment, the surface unevenness of the oxidefilm produces an anchor effect, allowing a plating film of a very goodadhesion property to be formed on the oxide film.

In one embodiment of the present invention, the oxide film is aconductive oxide film.

According to the above embodiment, a metal film can be formed on theconductive oxide film by electroplating by providing the oxide film bythe conductive oxide film.

In one embodiment of the present invention, the conductive oxide filmhas transparency.

According to the above embodiment, by providing the oxide film by aconductive oxide film having transparency, the transparent electrodeprovided for each pixel of, for example, a liquid crystal display deviceor a two-dimensional image detector besides the electricinterconnections can be formed of the same transparent conductive oxidefilm, allowing the reduction in number of processes to be achieved.

In one embodiment of the present invention, the metal film is either asingle layer film made of any one of nickel (Ni), copper (Cu) and gold(Au) or a multi-layer film including at least one layer of a singlelayer film made of any one of nickel (Ni), copper (Cu) and gold (Au).

According to the above embodiment, the Ni film can be formed on theoxide film (ITO film etc.) with a good adhesion property, andelectroless plating can be performed selectively on only the oxide film(ITO film etc.). Further, Cu and Au have a low specific resistance, andthis can achieve electric interconnections having a low resistance. Inparticular, by forming an Ni film on the oxide film (ITO film) andfurther forming a Cu, Au or Cu/Au film on the Ni film, then electricinterconnections having a low resistance and a good adhesion propertycan be provided.

In one embodiment of the present invention, a display device comprisesthe above interconnection substrates.

According to the above embodiment, a display device that can befabricated at low cost without using a vacuum film forming apparatus andis able to cope with a large-area substrate can be provided.

In one embodiment of the present invention, an image detector comprisesthe above interconnection substrates.

According to the above embodiment, an image detector that can befabricated at low cost without using a vacuum film forming apparatus andis able to cope with a large-area substrate can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1 is a sectional view of an interconnection substrate to be usedfor a display device according to a first embodiment of the presentinvention;

FIG. 2 is a perspective view showing the structure of an active matrixtype liquid crystal display device having the above interconnectionsubstrate;

FIGS. 3A through 3E are views showing a method for fabricating theelectric interconnections shown in FIG. 1;

FIG. 4 is a chart showing a procedure for forming a thin film made froma material of metallic alkoxide by the sol-gel method;

FIGS. 5A through 5C are sectional views of oxide film structures-varieddepending on the film forming method;

FIG. 6 is a sectional view of an interconnection substrate to be usedfor a display device according to a second embodiment of the presentinvention;

FIG. 7 is a sectional view of an interconnection substrate to be usedfor a display device according to a third embodiment of the presentinvention;

FIG. 8 is a schematic plan view of a two-dimensional image detectoraccording to a fourth embodiment of the present invention; and

FIG. 9 is a sectional view of one pixel of the above two-dimensionalimage detector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An electric interconnection fabricating method of the present invention,and a interconnection substrate, a display device and an image detectorusing the above method will be described in detail below on the basis ofembodiments shown in the drawings.

First Embodiment

FIG. 1 is a sectional view of an interconnection substrate to be usedfor the display device of the first embodiment of the present invention.

As shown in FIG. 1, a gate interconnection 2 and a gate electrode 3 areformed on a glass substrate 1 that serves as an insulating substrate.The gate interconnection 2 and the gate electrode 3 are constructed of alaminate film formed entirely by a wet type film forming techniqueaccording to an electric interconnection fabricating method describedlater, dissimilar to conventional electric interconnections of Al, Taand Mo formed by the sputtering method. A gate insulating film 4 made ofSiNx is further formed on the laminate film. A TFT portion 15 is formedon the gate electrode 3. The TFT portion 15 is constructed of a channellayer 6 made of a-Si:H, a contact layer 7 made of n+-type a-Si:H, asource electrode 8 made of Al (or Ta, Mo or the like) and a drainelectrode 9. Further, a transparent electrode 5 (or a reflectingelectrode) is formed in the pixel portion. An insulating overcoat 10made of SiNx and an organic insulating film are further formed on theTFT portion 15 and a bus line portion (the gate interconnection 2 and asource interconnection (not shown)). An interconnection substrateprovided with the aforementioned active element of TFT or the like isgenerally referred to as an active matrix substrate.

FIG. 2 is a perspective view showing a structure of an active matrixtype liquid crystal display device employing the above active matrixsubstrate. As shown in FIG. 2, gate electrodes 23 and source electrodes24 are arranged in a matrix form on an insulating substrate (an activematrix substrate) 21. A pixel electrode 25 and a TFT 26 are provided atevery intersection of the gate electrodes 23 and the source electrodes24. Color filters 34, a black matrix 35 and common electrodes 32 areprovided on a substrate 31 opposite to the active matrix substrate 21.The active matrix type liquid crystal display device has a structure inwhich liquid crystal 30 is interposed between the active matrixsubstrate 21 and the opposite substrate 31. In this active matrix typeliquid crystal display device, a transparent type liquid crystal displaydevice can be provided if a transparent electrode is employed as thepixel electrode 25, or a reflecting type liquid crystal display devicecan be provided if a reflecting electrode is employed as the pixelelectrode 25.

A method for fabricating the gate interconnection 2 and the gateelectrode 3 shown in FIG. 1 will be described next. FIGS. 3A through 3Eare process charts showing the method for fabricating the gateinterconnection 2 and the gate electrode 3. It is to be noted that onlya laminate film constructed of an ITO film 11, an Ni film 12, an Au film13 and a Cu film 14 is shown in connection with the gate interconnection2 and the gate electrode 3 of FIG. 1.

First Process

First, in a first process that serves as an oxide film forming process,an oxide thin film 42 is formed on the surface of an insulatingsubstrate 41 made of glass or the like by a wet type film formingtechnique, as shown in FIG. 3A. The insulating substrate of the presentinvention includes an inorganic substrate of glass, ceramic or asemiconductor substrate (or a conductor substrate) having a surfaceprovided with an insulating layer and a variety of organic substrates orfilms of polyethylene terephtalate (PET), acrylonitrile butadienestyrene copolymer (ABS) or polycarbonate (PC).

The wet type film forming technique of this first process is not the drytype film forming technique like the sputtering method or the CVD methodbut generally means the film forming techniques to be put into practiceusing no vacuum system. The above method includes, for example, thesol-gel method, the chemical deposition method or the liquid phasedeposition method with an aqueous solution, the coating film formationwith a solution or resin in which minute particles of oxide aredispersed, a chemical mist deposition (CMD) method with solution mistand spraying method.

The sol-gel method is to use an organic compound or an inorganiccompound of a metal in a solution, promote the hydrolysis andpolycondensation of the compound in the solution so as to fix the sol asgel and form an oxide solid by heating the gel.

FIG. 4 shows a procedure for forming a thin film made from metallicalkoxide by the sol-gel method. The metallic alkoxide capable of causinga polycondensation reaction is appropriate for the parent material.However, a metal salt, a metallic acetylacetonate complex or the likecan be used together with the metallic alkoxide. A variety of alcoholsare generally used as a solvent.

First, the metallic alkoxide is diluted with a solvent in Step S1.

Next, sol is formed by adding water to cause the hydrolysis andpolycondensation reactions in-Step S2.

Then, the sol is coated on the insulating substrate in Step S3,generating a gel film. In this case, there can be used a dipping method,a spin coating method and a meniscus coating method as the coatingmethod.

Subsequently, the gel film is dried and thereafter subjected to heattreatment at a temperature of above 400° C. in order to remove theremaining organic matter in Step S4, forming an amorphous or crystallinethin film.

Normally, the gel film obtained through the drying becomes amulti-porous body (xerogel) and tends to become a film in which minuteholes are existing in a network shape. By controlling the composition ofthe sol-gel solution and the sintering condition, the film can be formedinto an arbitrary form ranging from the multi-porous film in whichminute holes are existing in a network shape to a fine film having asmall number of holes.

If this kind of sol-gel method is used, then an oxide film can be formedmerely by coating the sol-gel solution on the insulating substrate ofglass or the like and sintering the same. This allows the film formationto be achieved using no vacuum film forming apparatus, allows aninterconnection substrate to be fabricated at low cost by forming ametal film on the oxide film and allows the method to cope with theformation of a large-area film.

The details of the sorts of the oxide film capable of forming a film bythe sol-gel method and the theory thereof are described in the documentof “Technology of Sol-Gel Method”(published by Agune Shoufusha, author:Sumio Sakka”) and other documents. The film formation of an ITO film, orthe transparent conductive oxide film is described by way of examples inthe document of “Preparation of ITO Thin Films by Sol-GelMethod”(Journal of the Ceramic Society of Japan, vol.102, NO.2,p.200-205, 1994) and the prior art reference of “Japanese PatentLaid-Open Publication No. HEI 8-253318”.

The chemical deposition method is to immerse an insulating substrate inan aqueous solution and deposit an oxide film on the insulatingsubstrate through a redox reaction in the aqueous solution and includesan anodic deposition method and a cathodic deposition method. By usingan oxidant and a reductant according to this chemical deposition method,an oxide film can be deposited on the insulating substrate in anelectroless manner. For example, if an insulating substrate to which acatalyst adheres is immersed in an aqueous solution in which a metallicnitrate and a reductant (for example, dimethylamine borane (DMAB))coexist, then a nitric-acid-to-nitrous-acid reduction reaction is causedby electrons supplied from the reductant, as a consequence of which ametal oxide film (or a hydroxide film) is deposited.

As a method for forming an oxide film in an aqueous solution, there is aliquid phase deposition method (LPD method). This liquid phasedeposition method is a method for depositing an oxide film on aninsulating substrate through the hydrolytic equilibrium reaction of ametallic fluoro-complex or hydrosilicofluoric acid.

By using the chemical deposition method described above, an oxide filmcan be formed by merely immersing a glass substrate in an aqueoussolution. This allows the oxide film formation to be performed using novacuum film forming apparatus, allows an interconnection substrate to befabricated at low cost by forming a metal film on the oxide film in asubsequent process and allows the method to cope with the formation of alarge-area film.

The formation of a ZnO film, or the transparent conductive oxide film isdescribed in the document of “Transparent Zinc Oxide Films ChemicallyPrepared from Aqueous Solution”(J. Electrochem. Soc., Vol.144, No.1,January 1997) and the prior art reference of “Japanese Patent Laid-OpenPublication No. HEI 9-278437”. The formation of an In₂O₃ film, or thetransparent conductive oxide film is described by way of examples in thedocument of “Preparation of Transparent Indium Oxide Films from aChemically Deposited Precursor” (Electrochemical and Solid-StateLetters, vol.1, No.5, 1998) and other documents.

The film coating of a solution or resin in which oxide minute particlesare dispersed is the method of dispersing ultrafine particles (particleshaving a primary particle diameter of about 0.01 to 0.1 μm) of atransparent conductive oxide in a binder of a photosensitive resist orthe like and forming a film on a substrate by the spin-coating method orthe like. According to the present method, a volumetric change such asthe contraction of a binder (i.e., resist resin) is caused by sinteringthe coated film at a temperature such that the binder is not thermallydecomposed. As a result, the dispersed ultrafine particles cohere tocome in contact with one another, effecting the performance of thetransparent conductive oxide film.

The coating film formation of the solution or resin in which theaforementioned oxide ultrafine particles are dispersed is described inthe prior art reference of “Japanese Patent Laid-Open Publication No.HEI 10-255556”. The film to be formed by the present method is not apure oxide film but a film of a mixture of the binder and the oxideultrafine particles, which is assumed to belong to the definition of theoxide film of the present specification in the broad sense.

Second Process

Next, in a second process that serves as a patterning process, there isperformed patterning of the oxide thin film 42 (shown in FIG. 3A)obtained through the first process according to an interconnectionshape, as shown in FIG. 3B.

The above patterning method is generally put into practice by forming aresist according to a specified pattern on the oxide film by thephotolithographic technique or the like and removing the unnecessaryoxide film by wet etching or dry etching. For example, HBr or a ferricchloride aqueous solution can be used for the etching of the ITO film. Azinc catalyst and hydrochloric acid can be used for the etching of SnO₂.

When otherwise forming an oxide film by the sol-gel method in the firstprocess, it is also acceptable to make the oxide film itself havephotosensitivity and perform patterning using no resist. For example, ifa gel film is formed by using metallic alkoxide chemically decoratedwith a chelating agent of acetylacetone (AcAc), benzoylacetone (BzAc) orthe like, then the solubility of the gel film is largely changed byultraviolet ray application. That is, the chelate bond of the gel filmto which the ultraviolet rays are applied becomes cut and insoluble inan alkaline solution or alcohol. By performing exposure and developmentof the gel film and thereafter sintering the resulting object accordingto this theory, the patterning of the oxide film becomes simplified. Itis also acceptable to perform the patterning through the decompositionof the gel film by applying excimer laser light to the normal gel filmthat has not been chemically decorated.

According to another method, it is enabled to give photosensitivity tothe sol-gel solution by blending the sol-gel solution with a resinhaving photosensitivity at an appropriate rate. If ultraviolet rays areapplied to the precursor film of the material obtained by blending amonomer (for example, acrylic monomer) having photopolymerizability tothe sol-gel solution with a polymerization initiator, then the monomeris polymerized to form a polymer in a network shape (polymer network),and the sol-gel solution exists in the spaces of the polymer network.Subsequently, by performing a developing process, only the film in thepolymer portion to which the ultraviolet rays are applied is left as anegative pattern, and the sol-gel solution is also dissolved in thedeveloping solution together with the monomer that has not beenpolymerized in the portion to which the ultraviolet rays have not beenapplied. Finally, by performing sintering at a temperature of about 500°C. so as to remove the remaining organic matter in the polymer networkand the sol-gel solution, a sol-gel oxide film pattern is completed. Inthis case, a negative type photoresist or the like on the market can beused as this photosensitive resin.

Third Process

Next, in a third process that serves as a metal film forming process, ametal film 43 made of Ni is formed on an oxide film pattern 42 a (shownin FIG. 3B) obtained through the second process by a wet type filmforming technique, as shown in FIG. 3C. The wet type film formingtechnique in this third process is not the dry type film formingtechnique like the sputtering method or the CVD method but generallymeans the film forming technique to be put into practice using no vacuumsystem, i.e., the so-called wet type plating method.

The wet type plating method is classified roughly into electroplatingand electroless plating.

In the case of the electroplating, a metal film is deposited on thecathode surface by arranging a metal that serves as an anode and acathode (electrode to be plated) in a plating liquid in which metal ionsare dissolved and flowing a direct current through the plating liquid.Therefore, if the oxide film formed in the first process hasconductivity, then a metal film can be deposited on only the oxide filmby using the oxide film as the cathode.

In the case of electroless plating (reduction plating, displacementplating or the like), a metal film can be deposited flowing no currentthrough the plating liquid. Therefore, a metal film can be depositedregardless of the conductivity of the oxide film formed through thefirst process. Further, by performing the treatment of making thecatalyst adhere to the surface of only the oxide film or preparatorilymaking the oxide film contain a plating catalyst of Pd or the like inthis stage, a metal film can also be selectively deposited on only theoxide film.

A metal that can be plated by the wet type plating method can beprovided by nickel, cobalt, tin, gold, copper, silver or palladium. Themetal film to be formed through this third process may be a single layeror a laminate film of metal films having different roles. For example,it is acceptable to laminate a metal film 44 made of Au having a lowresistance by electroless plating on the metal film 43 made of Niexhibiting a good adhesion to the oxide film (FIG. 3D) and furtherlaminate by electroplating a metal film 45 made of Cu that has a lowresistance and costs less on the Au film 44 (FIG. 3E).

As described above, through the first process, the second process andthe third process, electric interconnections of a laminate structureformed of a metal film and an oxide film can be obtained without usingany vacuum film forming apparatus.

In the case where a metal film is formed on an ITO pattern, the metalfilm has conventionally been formed by the plating technique using novacuum film forming apparatus. However, with regard to the ITO film thatbecomes the groundwork of the metal film, the film formation has stillbeen performed by a vacuum film forming apparatus according to thesputtering method or the deposition method. Therefore, the merits of thecost reduction effect and the easiness of the formation of a large-areafilm have not been sufficiently obtained.

In contrast to this, according to the aforementioned electricinterconnection fabricating method, which uses no vacuum film formingapparatus, leads to a low apparatus cost, allowing a sufficient costreduction effect to be obtained as compared with the conventionalelectric interconnection fabricating method. Furthermore, the wet typefilm forming technique, which can easily form a large-area film bycomparison with the vacuum film forming technique, can easily cope witha large-area substrate. Furthermore, film formation at low temperaturecan be achieved, and this allows the reduction in quantity of energyconsumption relevant to the film formation.

In regard to the aforementioned first process through the third process,specific four interconnection substrate fabricating methods (1) through(4) will be described below.

Electric Interconnection Fabricating Method (1)

First, as a first process, an ITO film is formed by the sol-gel methodon a glass substrate of #1737 produced by Corning Corp. In this stage, asol-gel solution is diluted with alcohol to an appropriate viscosity andcoated to a thickness of about 0.2 μm by the spin-coating method. Then,by performing drying at a temperature of 150° C. and sintering at atemperature of 450° C., a multi-porous ITO film having a thickness ofabout 0.1 μm is completed.

Next, as a second process, the patterning of the ITO film is performed.A positive type photoresist is. coated to a thickness of about 1 μm onthe ITO film by the spin-coating method, thereafter subjected topre-baking at a temperature of 80° C. and thereafter exposed toultraviolet rays via a photomask. Subsequently, by performing adeveloping process and a post-baking process at a temperature of 120°C., a resist pattern having an interconnection shape is formed on theITO film. By immersing the glass substrate on which this resist patternis formed in HBr, the ITO film is etched within the region that is notcovered with the resist. Finally, by removing the resist by means of aresist removing liquid, an ITO pattern of the interconnection shape isformed.

Further, as a third process, an Ni film is formed on the ITO film byelectroless plating. First, the insulating substrate provided with anITO pattern is subjected to degreasing and cleaning by means of alkaliand an organic solvent. Next, by slightly roughening the ITO filmsurface by etching with a fluoride-containing solution as the occasiondemands and thereafter performing an activating treatment by immersionin a palladium chloride solution, a palladium catalyst that becomes thecatalyst for electroless plating is deposited on only the ITO film.Then, the Ni film is formed to a thickness of about 0.3 μm by means ofan electroless Ni plating liquid using hypophosphite as a reductant.Through this process, the Ni film is selectively formed on only the ITOpattern.

As a method for providing a palladium catalyst, it is also allowed todeposit a palladium catalyst selectively on only the ITO film through acatalyst providing process with a complex salt made of PdCl₂ or SnCl₂ ora colloid solution and a catalyst accelerating process with acidaccelerator containing fluoride.

By incorporating a catalyst of Pd or the like into the oxide filmobtained by the sol-gel method or forming an oxide film made principallyof PdO, the aforementioned catalyst providing process can also beeliminated.

In general, the oxide film obtained by the sol-gel method can be formedas a fine film having a small number of holes. However, by controllingthe composition of the sol-gel. solution and the sintering condition, amulti-porous film in which minute holes exist in a network shape canalso be obtained. That is, by comparison with the smooth surface shapeof an ITO film 52 formed on a glass substrate 51 by the sputteringmethod as shown in FIG. 5A, an ITO film 54 that is formed on aninsulating substrate 53 by the sol-gel method and internally has manyholes 55 can be obtained as shown in FIG. 5B. As described above, in thecase of the ITO film 54 that is intentionally formed multi-porous, thepalladium catalyst for electroless plating is also deposited inside theminute holes of the ITO film 54, and Ni is deposited so as to fill upthe holes. Therefore, the minute holes of the ITO film 54 produce ananchor effect, and a plating film having a good adhesion property can beobtained by comparison with the Ni plating on the ITO film 54 obtainedthrough vacuum film formation such as sputtering.

For the sake of comparison, the ITO film formed by the sputtering methodand the ITO film formed by the sol-gel method were subjected toelectroless plating with Ni under same conditions without performing thesurface roughening process by etching of the ITO film and to theevaluation of the adhesion property through a peeling test by across-cutting method. As a result, Ni plated on the ITO film formed bythe sputtering method exhibited a partial exfoliation phenomenon,whereas Ni plated on the ITO film formed by the sol-gel method exhibitedno film exfoliation.

The thus obtained electroless Ni plating film becomes an eutectoid filmof Ni and P under the influence of the reductant. Therefore, the filmhas a high surface resistance of 4 to 5 Ω/▭ and is able to be limitedlyused for the electric interconnections. Therefore, in order to reducethe resistance of the Ni film, the Ni film is plated with Au as theoccasion demands.

This Au plating is able to perform electroless plating on the Ni film,and therefore, a film can be selectively formed on only the Ni/ITO filmhaving an interconnection shape. By replacing the Ni film with Au to adepth of about 0.5 μm from the surface, the surface resistance of thefilm can be reduced to a resistance of about 0.5 Ω/▭.

Further, if resistance reduction is required, then it is proper toincrease the film thickness of Au by electroplating or form alow-resistance film of Cu or the like on the Au film by metalelectrolysis (or electroless plating). It is to be noted that theincrease in thickness of Au plating leads to a cost increase, andtherefore, it is preferable to reduce the resistance by Cu plating. Forexample, if a Cu film is formed to a thickness of about 0.15 μm on anAu/Ni/ITO film by Cu electroplating, then the surface resistance of thefilm is reduced to about 0.1 Ω/▭, and the film can be sufficiently usedfor the electric interconnections of a large-size high-definition flatpanel display.

In this case, the electric interconnections come to have a structure inwhich Cu is exposed on the surface. However, in order to prevent theoxidation of Cu, it is of course useful to protect Cu until the nextprocess by further laminating a barrier metal or coating an oxygeninterrupting film.

The plating film to be formed on the ITO film is not limited to theabove, and it is also acceptable to use a variety of metals of nickel,cobalt, tin, gold, copper, silver or palladium or a combination of thesesubstances for the film.

Electric Interconnection Fabricating Method (2)

Similarly to the first and second processes of the fabricating method(1), an ITO film is formed by the sol-gel method and the ITO film ispatterned by etching. By controlling the composition of the sol-gelsolution and the sintering conditions when forming an oxide film, amulti-porous film in which minute holes exist in a network shape insidethe oxide film is formed.

Subsequently, as a third process, a metal film is formed on the ITOfilm. Specifically, a palladium catalyst is deposited selectively ononly the ITO film through a catalyst providing process with a complexsalt made of PdCl₂ or SnCl₂ or a colloid solution and a catalystaccelerating process with an acid accelerator containing fluoride. Inthis stage, a palladium catalyst is deposited inside the minute holes ofthe ITO film.

Subsequently, a Cu film is formed to a thickness of 0.2 μm on the ITOfilm by - electroless plating. Conventionally, the electroless platingof the ITO film with Cu has had a very bad adhesion property and theformation of a Cu film has been difficult. However, according to thisfabricating method (2), the minute holes of the ITO film formed by thesol-gel method produce an anchor effect, and this allows direct Cuplating on the ITO film to be achieved. By utilizing this theory, theITO film can be directly plated with not only Cu but also another metalsuch as Au.

With this arrangement, the surface resistance of the Cu/ITO film becomesabout 0.1 Ω/▭, and the film can be sufficiently used for the electricinterconnections of a large-size high-definition flat panel display.

Electric Interconnection Fabricating Method (3)

First, as a first process, an SnO₂ film is formed by the sol-gel methodon a glass substrate of #1737 produced by Corning Corp. In this stage, asol-gel solution is blended with acetylacetone (AcAc), diluted withalcohol to an appropriate viscosity and coated to a thickness of about0.1 μm by the spin-coating method. Then, the resulting object is driedat a temperature of about 200° C. so as to form an SnO₂ chelate film.

Next, as a second process, the SnO₂ chelate film is patterned.Specifically, by applying ultraviolet rays (λ=300 nm) to the SnO₂chelate film via a photomask on which an interconnection pattern isdrawn, the chelate bond of only the portion to which the ultravioletrays are applied is cut. Subsequently, if the insulating substrate isimmersed in an alkaline solution, then only the chelate film that hasnot been exposed to ultraviolet rays is dissolved, and the SnO₂ patternis consequently completed. Subsequently, by performing sintering at atemperature of about 400° C., the SnO₂ is made to be fine and have a lowresistance, completing the SnO₂ interconnection pattern.

Next, as a third process, a metal film is formed on the SnO₂ film byplating. As a plating film forming method, a method similar to those ofthe aforementioned fabricating methods (1) and (2) can be used with thefollowing structure of:

Ni/SnO₂ film,

Au/Ni/SnO₂ film,

Cu/Au/Ni/SnO₂ film,

Cu/Ni/SnO₂ film, or

Cu/SnO₂ film.

Particularly, by employing a film construction using Cu or Au, thesurface resistance of the film becomes about 0.1 Ω/▭, and the film canbe sufficiently used for the electric interconnections of a large-sizehigh-definition flat panel display.

The aforementioned electric interconnection fabricating method (3),which requires neither resist coating process nor resist removingprocess between the film formation of the SnO₂ film and the patterning,has an improved fabrication efficiency as compared with the fabricatingmethod (1).

As a sol-gel oxide film that can provide photosensitivity using achelating agent, there can be formed a variety of oxide films made ofIn₂O₃, ITO, TiO₂, ZrO₂ and SiO₂ besides the aforementioned SnO₂ film. Bymaking a catalyst selectively adhere to the surface of the oxide film, avariety of metal films can be selectively formed by plating on the oxidefilm pattern.

Electric Interconnection Fabricating Method (4)

First, as a first process, a ZnO film is formed by the chemicaldeposition method on a glass substrate of #1737 produced by CorningCorp. Describing in concrete this process, the ZnO film is formed to athickness of 0.2 μm by first degreasing and cleaning a glass substratewith an alkaline solution and an organic solvent, providing a palladiumcatalyst through a process with a sensitizer and an activator andthereafter immersing the resulting substrate in an aqueous solutioncontaining Zn(NO₃)₃ and dimethylamine borane (DMAB) at a bathtemperature of 60° C. (refer to the prior art reference of JapanesePatent Laid-Open Publication No. HEI 9-278437 for the detail of the filmforming process).

In this case, the film is formed around a core of palladium, or thecatalyst. Therefore, a significant unevenness exists on the surface bycomparison with the oxide film formed by a vacuum film formingapparatus. That is, as shown in FIG. 5C, there can be obtained a ZnOfilm 57 that is formed on the insulating substrate 56 by the chemicaldeposition method and has surface unevenness.

Next, as a second process, the ZnO film is patterned according to aninterconnection shape through an etching process using a resist mask.

Next, as a third process, a metal film is formed on the ZnO film byplating. As a plating film forming method, a method similar to those ofthe aforementioned fabricating methods (1) and (2) can be used with thefollowing structure of:

Ni/ZnO film,

Au/Ni/ZnO film,

Cu/Au/Ni/ZnO film,

Cu/Ni/ZnO film, or

Cu/ZnO film.

Particularly, by employing a film construction using Cu or Au, thesurface resistance of the film becomes about 0.1Ω/▭, and the film can besufficiently used for the electric interconnections of a large-sizehigh-definition flat panel display.

A similar plating film can be obtained by employing an ITO film obtainedby the chemical deposition method in place of the ZnO film.

The surface unevenness of the oxide film obtained by the chemicaldeposition method as in the case of the aforementioned ZnO film and ITOfilm produces an anchor effect, allowing a plating film having a verygood adhesion property can be obtained.

For the sake of comparison, the ITO film formed by the sputtering methodand the ZnO film formed by the chemical deposition method were bothsubjected to electroless plating with Ni under same conditions withoutperforming the surface roughening process by etching of the ITO film andto the evaluation of the adhesion property through a peeling test by thecross-cutting method. As a result, Ni plated on the ITO film formed bythe sputtering method exhibited a partial exfoliation phenomenon,whereas Ni plated on the ZnO film formed by the chemical depositionmethod exhibited no film exfoliation.

As a method for forming an oxide film in an aqueous solution, there is aliquid phase deposition method using the hydrolytic equilibrium reactionof a metallic fluoro complex or hydrosilicofluoric acid besides thechemical deposition method using the aforementioned redox reaction, andthe formation of a variety of oxide films made of SiO₂ or TiO₂ can beachieved.

By making the catalyst selectively adhere to the surface of these oxidefilms, a variety of metal films can be selectively formed by plating onthe oxide film pattern.

The oxide film is deposited in an aqueous solution according to theaforementioned electric interconnection fabricating method (4), andtherefore, film formation can also be achieved at a low temperature ofnot higher than 100° C. The metal film to be formed by plating on theoxide film can also be formed at a low temperature of not higher than100° C., and therefore, electric interconnections can be entirely formedthrough the low temperature process of not higher than 100° C. exceptfor auxiliary sintering after the film formation in order to improve theadhesion property. Therefore, the substrate is not limited to the glasssubstrate, and electric interconnections can be easily formed on anorganic substrate (or film) of ABS, PC, PET or the like.

The electric interconnection fabricating methods (1) through (4), whichdo not use any vacuum film forming apparatus, can obtain a sufficientcost reduction effect by comparison with the conventional electricinterconnection fabricating method. The wet type film forming technique,which can form a large-area film easier than the vacuum film formingtechnique, can easily cope with a large-area substrate. Furthermore,electric interconnections can be formed with high productivity accordingto a roll-to-roll system while continuously transferring a very longfilm material wound in a roll form taking advantage of the merit ofusing no vacuum system.

According to the first embodiment of the present invention, the electricinterconnections are formed by forming the metal film by electrolessplating on the oxide film obtained entirely by the wet type film formingtechnique. However, if a conductive oxide film is used as the oxidefilm, then a plating film can be formed directly on the conductive oxidefilm also by electroplating instead of electroless plating. It is to benoted that the distribution in film thickness of the plating film isinfluenced by the sheet resistance of the conductive oxide film in thiscase, and therefore, the substrate size and applications are limitedtaking the above factor into consideration.

According to the first embodiment, a metal film of an excellent adhesionproperty can be formed by providing a metal plating on the oxide filmformed by the sol-gel method and the chemical deposition method ratherthan by providing a metal plating on the oxide film formed by thesputtering method and the deposition method using a vacuum film formingapparatus. Therefore, a display device having excellent reliability canbe provided.

Second Embodiment

FIG. 6 is a sectional view of an interconnection substrate to be usedfor the display device of the second embodiment of the presentinvention. This interconnection substrate is an active matrix substratefor a liquid crystal display device that employs the electricinterconnections fabricated by any one of the electric interconnectionfabricating methods (1) through (4) of the first embodiment.

As shown in FIG. 6, a gate interconnection 82 (gate electrode 83) isformed on a glass substrate 81, and the electric interconnectionfabricating methods (1) through (4) can be simply adopted in place ofthe conventional electric interconnections of Al, Ta or Mo formed by thesputtering method (FIG. 6 shows only the electric interconnectionconstructed of a laminate film having a four-layer structure). A gateinsulating film 84 made of SiNx is further formed on theinterconnection. A TFT portion 80 constructed of a channel layer 85 madeof a-Si:H, a contact layer 86 made of n+-type a-Si:H, a source electrode87 made of Mo and a drain electrode 88 is formed on the gate electrode83. An insulating protective film 101 made of SiNx and an organicinterlayer insulating film 103 are further formed on the TFT portion 80and the bus line portion (the gate interconnection 82 and a sourceinterconnection (not shown)). A transparent electrode 89 (or areflecting electrode) is further formed as a pixel electrode in theuppermost layer of the organic interlayer insulating film 103. Thetransparent electrode 89 that is the pixel electrode and the drainelectrode 88 are electrically connected to each other via a contact hole104 provided between the insulating protective film 101 and the organicinterlayer insulating film 103.

The interconnection substrate having the aforementioned construction hasan effect similar to that of the interconnection substrate of the firstembodiment shown in FIG. 1.

Third Embodiment

FIG. 7 is a sectional view of an interconnection substrate to be usedfor the display device of the third embodiment of the present invention.This interconnection substrate is an active matrix substrate for aliquid crystal display device that employs the electric interconnectionsfabricated by any one of the fabricating methods (1) through (4) of thefirst embodiment.

As shown in FIG. 7, a gate interconnection 92 (gate electrode 93) isformed on a glass substrate 91, and the electric interconnectionfabricating methods (1) through (4) are adopted in place of theconventional electric interconnections of Al, Ta or Mo formed by thesputtering method (FIG. 7 shows only the electric interconnectionconstructed of a laminate film having a four-layer structure). In thiscase, an oxide film that serves as the lowermost layer of the gateinterconnection 92 has preparatorily been formed of a conductive oxidefilm made of ITO, SnO₂ or ZnO and a pixel electrode 94 has preparatorilybeen formed concurrently with the formation of this conductive oxidefilm. A gate insulating film 100 made of SiNx is further formed on theinterconnection. A TFT portion 90 constructed of a channel layer 96 madeof a-Si:H, a contact layer 97 made of n+-type a-Si:H, a source electrode98 made of a metal of Mo, Ta or Al and a drain electrode 99 is formed onthe gate electrode 93. An insulating protective film 102 made of SiNx oran organic interlayer insulating film is formed on the TFT portion 90and the bus line portion (the gate interconnection 92 and a sourceinterconnection (not shown)).

If the conductive oxide film made of ITO, SnO₂, ZnO or the like havingexcellent transparency is employed as the oxide film located in thelowermost layer of the gate interconnection 92, then the electricinterconnections and the separately provided transparent conductive film(for example, the transparent electrode provided for each pixel), whichare both required to be formed as in the case of a liquid crystaldisplay device, can be formed of an identical transparent conductiveoxide film, allowing the reduction in number of processes (for higherefficiency) to be achieved.

Fourth Embodiment

FIG. 8 shows a schematic plan view of the two-dimensional image detectorof the fourth embodiment of the present invention. As shown in FIG. 8,the two-dimensional image detector is provided with a glass substrate110, pixel electrodes 111 arranged in a matrix form on the glasssubstrate 110, a gate interconnection 112 provided for each row of thepixel electrodes 111, a data electrode 113 provided for each column ofthe pixel electrodes 111, an amplifier 114 whose input terminal isconnected to the data electrode 113, a TFT 115 whose gate is connectedto the gate interconnection 112 and a storage capacitor 116 provided foreach pixel electrode 111.

FIG. 9 is a sectional view of one pixel of the Um two-dimensional imagedetector shown in FIG. 8. This two-dimensional image detector basicallyhas a structure in which an X-ray conductor and an upper electrode areformed on an active matrix board. As shown in FIG. 9, a gate electrode122 is formed on a glass substrate 121. This gate electrode 122 isconstructed of a laminate film of Cu/Au/Ni/ITO formed entirely by thewet type film forming technique described in connection with the firstembodiment, dissimilar to the conventional electric interconnections ofAl, Ta or Mo formed by the sputtering method. A gate insulating film 124made of SiNx is further formed on the interconnections. A TFT portion120 constructed of a channel layer 126 made of a-Si:H, a contact layer127 made of n+-type a-Si:H, a source electrode 128 made of a metal ofAl, Ta, Mo or the like and a drain electrode 129 is formed on the gateelectrode 122. An insulating layer 130 made of a resin is further formedso as to cover the TFT portion 120, the gate interconnection and asource interconnection (not shown), and thereafter, a transparentelectrode and a metal electrode are formed as a pixel electrode 128. Thepixel electrode 128 and the drain electrode 129 of the TFT portion 120are connected to each other by way of a via hole (not shown) providedthrough the insulating layer. The storage capacitor is comprised of thegate insulating film 124 interposed between a storage capacitorelectrode 123 and the pixel electrode 128.

By forming an X-ray conductive layer 131 and an upper electrode 132 onthe active matrix substrate having the aforementioned construction, atwo-dimensional image detector is completed. It is to be noted thata-Se, CdTe, CdZnTe, PbI₂ or the like can be used as the material of theX-ray conductive layer 131.

If X-rays are incident on the X-ray conductive layer in thetwo-dimensional image detector having the aforementioned construction,then an electron-hole pair is generated inside the X-ray conductivelayer 81, and the electric charges are accumulated in the storagecapacitor (constructed of the storage capacitor electrode 123, the pixelelectrode 128 and the gate insulating film 124). By successively readingthe electric charges by the TFT portion 120 (115 in FIG. 8) arranged inthe two-dimensional shape, an X-ray image can be obtained.

As described above, electric interconnections (gate interconnections) ofa laminate structure formed of a metal film and an oxide film can beobtained in the aforementioned two-dimensional image detector withoutusing any vacuum film forming apparatus. Therefore, a metal film havingan excellent adhesion property can be formed on the oxide film similarlyto the first through third embodiments. Therefore, a two-dimensionalimage detector of high reliability can be provided.

According to this fourth embodiment, no vacuum film forming apparatus isused. Therefore, the apparatus cost is low, and a sufficient costreduction effect by comparison with the conventional electricinterconnection fabricating method can be obtained. The wet type filmforming technique, which can form a large-area film more easily than thevacuum film forming technique, can easily cope with a large-areasubstrate. In particular, if it is tried to detect a two-dimensionalimage of X-rays, then a two-dimensional image detector of a size roughlyequal to that of the image receiving area is necessary since it istheoretically difficult to form an X-ray image. Accordingly, it isrequired to increase the area of the two-dimensional image detectoritself, and therefore, the present invention can be evaluated as veryeffective. Furthermore, low-temperature film formation can be achieved,and therefore, the quantity of energy consumption relevant to the filmformation can also be reduced.

Furthermore, the X-ray conductive layer may be patterned so as to beseparated every pixel, and the X-ray conductive layer is also made ableto have a variety of diode structures. If a photoconductive layer isused in place of the X-ray conductive layer, then a two-dimensionalimage detector sensitive to visible light can be formed. Furthermore, itis able to construct a two-dimensional image detector sensitive toX-rays can be constructed by-combining the two-dimensional imagedetector sensitive to visible light and an X-ray-to-light-convertinglayer.

It is to be noted that the structures of the interconnection substrates(active matrix substrates) shown in FIG. 1, FIG. 6, FIG. 7 or FIG. 9 ofthe first through fourth embodiments are mere examples, and a wet typefilm forming technique can be used for not only the gate interconnectionbut also the source interconnection. The TFT structure is limited toneither one of the TFT portions 15, 80, 90 and 120 shown in FIG. 1, FIG.6, FIG. 7 and FIG. 9, and the structure can be applied to either one ofa stagger structure or a reverse stagger structure. It is acceptable toadopt not only the TFT employing a-Si but also a TFT structure employinganother semiconductor film made of p-Si, CdSe or the like. Further, anactive matrix substrate employing Metal Insulator Metal (MIM),back-to-back diode (BTB), a diode ring, a varistor, a plasma switchingor the like may be broadly used for a display device or an imagedetector besides TFT. The structure of the electric interconnections canalso be used for an interconnection substrate provided with no activeelement, and a passive matrix type display device can be formed byemploying the interconnection substrate.

The liquid crystal display device employing the interconnectionsubstrate has been described in connection with the first through thirdembodiments. However, the display device is not limited to this, and thepresent invention can be applied to display devices employing an opticalmedium other than liquid crystal as a display medium and to, forexample, display devices that need electric interconnections, such as:

plasma display devices (PDP),

inorganic or organic EL display devices,

electrochromic display devices, and

electrophoretic display devices.

The present invention can be widely applied, among others, to displaydevices that require resistance reduction, areal increase and costreduction.

The electric interconnection fabricating method of the present inventioncan be widely applied to flat panel display devices of an active matrixdrive type and a passive matrix drive type, two-dimensional imagedetectors having a flat panel shape and other electric equipmentprovided with electric interconnections.

The interconnection substrate (active matrix substrate) of the presentinvention can be used for transparent type liquid crystal displaydevices, reflecting type liquid crystal display devices andtwo-dimensional image detectors. Among others, the interconnectionsubstrate is very effective for the case of Cu used to reduce theresistance of the electric interconnections or the case of formation ofelectric interconnections by the wet type film formation instead of thedry type film formation, as in the field of display devices required tohave a large area.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. An interconnection substrate having electricinterconnections comprising: an insulating substrate provided with aplating catalyst in a surface thereof; an oxide film comprised of ZnOand formed on the surface of the insulating substrate provided with theplating catalyst; and a metal film formed on the oxide film.
 2. Theinterconnection substrate as set forth in claim 1, wherein the oxidefilm has a surface in contact with the metal film, the surface having atleast one surface property selected from the group consisting of aporous surface and an uneven surface, and wherein adhesion of the metalfilm to the oxide film is improved by an anchor effect of the at leastone surface property of the oxide film.
 3. The interconnection substrateas set forth in claim 1, wherein the metal film is either a single layerfilm made of any one of nickel (Ni), copper (Cu) and gold (Au) or amulti-layer film including at least one layer made of any one of nickel(Ni), copper (Cu) and gold (Au).
 4. The interconnection substrate as setforth in claim 1, wherein the oxide film is patterned according to ashape of the interconnections and wherein the metal film is formedselectively on the patterned oxide film.
 5. The interconnectionsubstrate as set forth in claim 1, wherein the oxide film is aconductive oxide film.
 6. The interconnection substrate as set forth inclaim 5, wherein the conductive oxide film has transparency.
 7. Adisplay device comprising the interconnection substrate set forth inclaim
 1. 8. An image detector comprising the interconnection substrateset forth in claim 1.